I should say I tend to look for stalemate lines on the go, so the ones I've found thus far have been ones relevent to games I've been in. There are a lot more than this.
If you're looking to become uneliminatable as an eastern power (China, Turan, India, Srivijaya) then you can form a minimal stalemate line with 20 centers:
(Starts at Silla, just east of China's start, goes west and then south after reaching Ujjain)
A Sil
F YeS
A Hen & A Sic S A ChA
A Tib S A Amd
A Nep S A Kas
A Ind S A Sha
A Knj & A Ras S A Ujj
A Cho H
F Cor H
F Ser H
F Min & F Jam S F SuS
20 units
Holds 20 centers (Ser, Cho, Ujj, Knj, Ind, Kas, Var, Tib, Pag, ChA, Nan, Gua, Sil, Sai, Kam, Cah, Jam, Plm, Kal, But)
Once you start getting boardwide effort to stop a major power or alliance, you can defend many more centers using almost the same number of units:
(Starting from the Western Sea, just west of Wagadu's starting location, and stretching West to East)
F WtS H
F Tka & F Mau S F STa
A Kut & A Tah S A Ifr
A Tri S A Bar
A Ale & A Mec S A Jer
A Oma & A Yem S A Nef
F Ara-Bsr (prevent transformation to fleet, if it ever moves, move it back again next turn)
A Sha S A Man
A Amd & A Kas S A Sog
A Hen S A Yan
F YeS S A Blh
25 units
45 Centers (Tka, Awl, KuS, Nio, Wal, JeJ, Mau, Ifr, Zaw, Kan, Bar, Ale, AQa, Mak, Axu, Adu, Roh, Mal, Zim, Mah, Jer, Yem, Soc, Man, Ujj, Ind, Knj, Kas, Tib, Var, Cho, Ser, Plm, Jam, Kal, Cah, But, Kam, Pag, Gua, ChA, Nan, Yan, Sai, Sil)
If you're stalemating a single player and not an alliance, your stalemate line must control at least 55 centers to prevent the solo. There are a number of places you can extend the line forwards - the most unit efficient is probably pushing forward into 3 of the mediterreanean islands and 7 of the easily claimed centers in front of the Asian part of the previous line:
(Again starting at Western Sea, stretching west to east)
F WtS H
F Tka & F Mau S F STa
A Kut S A Ifr
F LiS S F Sic (& vice versa)
F EgS & F Cre & F Cyp S F CiS
F STy & A Jer S A Dam
A Nef S A Bag
A Bas S A Isf
A Sjs S A Kho
A Her S A Buk
A Blk & A Uyg S A Sam
A Yan S A Chn
A YeS S A Blh
30 units
Holds 55 centers (all those of the previous line + Sic, Cre, Cyp, Bag, Isf, Bas, Her, Buk, Sam, Uyg).
It's easy to see that centers like OrB could be easily added to a line like this - just as in Classic, the more centers you control, the easier it will be to form a stalemate line. This is the minimal unit east-west line that protects exactly 55 centers though (I think).
There are a fair few North-South lines too, but I've spent enough time typing these out today :D